1. Field of the Invention
This invention relates to a 4-stroke cycle internal combustion engine which includes a breather chamber.
2. Description of Background Art
In an internal combustion engine, it is desirable to separate a mixture of blow-by gas leaking from a combustion chamber into a crank chamber and oil mist scattered in the internal combustion engine from each other by means of a breather chamber and introduce, in a blow-by gas reduction apparatus for introducing the blow-by gas to an intake system, the blow-by gas into the breather chamber under an environment in which there is a little oil mist.
A 4-stroke cycle internal combustion engine is known wherein a breather plate is interposed between an upper portion of a head cover and a valve chamber which accommodates a valve motion and a breather chamber is formed between the head cover and the breather plate. See, for example, Japanese Utility Model Laid-Open No. Hei 5-77522.
In the vertical 4-stroke cycle internal combustion engine disclosed in Japanese Utility Model Laid-Open No. Hei 5-77522, a plate member is interposed between a cylinder head cover with a valve motion disposed below the cylinder head cover such that a breather chamber is formed below the cylinder head cover by the plate member.
In order to separate oil mist generated in the valve motion below the plate member and a valve motion system power transmission mechanism for transmitting valve driving power from the crankshaft to the valve motion from blow-by gas, a plate member is provided so as to extend from a power transmission mechanism provided at one end of a camshaft to the other end of the camshaft with the opposite side portions of the plate member being bent perpendicularly downwardly at a fold extending in parallel to the camshaft.
In the internal combustion engine disclosed in Japanese Utility Model Laid-Open No. Hei 5-77522, the plate member extends sidewardly of a sprocket wheel, this extension does not play a role in preventing oil mist generated in a valve motion system power transmission mechanism from being scattered in a direction toward the entrance of the breather chamber. Therefore, the internal combustion engine has a problem in that an environment with a small amount of oil mist cannot be produced. Thus, the breather performance is dropped.
Further, since the plate member is provided so as to extend over the substantially overall length of the cylinder head cover, the height of the internal combustion engine is increased by the height of the breather chamber, which is disadvantageous in terms of miniaturization of the internal combustion engine.